Female-specific wing degeneration is triggered by ecdysteroid in cultures of wing discs from the bagworm moth, Eumeta variegata (Insecta: Lepidoptera, Psychidae)

Female adults of the bagworm moth, Eumeta variegata, are completely wingless; by contrast, the male adults have functional wings. Sex-specific differences in the development of wing discs appear to arise during the 8th (penultimate) larval instar. We have previously found that the wing discs of female E. variegata terminate development and disappear during the prepupal period, whereas the wing discs of males continue to develop fully into adult wings. We have investigated the effects of ecdysteroid (20-hydroxyecdysone, 20E) when cultured with larval wing discs, which are normally attached to the larval integument of both male and female larvae. Male wing discs cultured with 20E undergo a remarkable transformation: the discs undergo apolysis and then differentiation. Female wing discs cultured with 20E also undergo apolysis; however, the disc cells enter apoptosis. We have observed condensed chromatin, fragmented nuclei, and secondary lysosomes in the epithelial cells of these female discs. This report establishes that the reduction of female wing discs arises through apoptotic events triggered by ecdysteroid in vitro.     

Association of the polymorphisms in the 5'-untranslated region of PTEN gene with type 2 diabetes in a Japanese population

Phosphatase and tensin homolog deleted on chromosome 10 (PTEN) is known to act as a lipid phosphatase hydrolyzing phosphatidylinositol (PI)(3,4,5)P(3) to PI(4,5)P(2). Since the PI3-kinase product, PI(3,4,5)P(3), is an important second messenger leading to the metabolic action of insulin, PTEN functions as a potent negative regulator of insulin signaling and its gene is one of the possible candidates involved in susceptibility to the development of type 2 (non-insulin-dependent) diabetes. In the present study, we investigated the polymorphisms of the PTEN gene in Japanese patients with type 2 diabetes and non-diabetic control subjects. We identified three mutations of the gene in the type 2 diabetes patients. Among these mutations, the frequency of the substitution of C with G at position -9 (-9C-->G) (SNP1), located in the untranslated region of exon 1, was significantly higher in type 2 diabetic patients than in control subjects. In addition, transfection of the PTEN gene with SNP1 resulted in a significantly higher expression level of PTEN protein compared with that of the wild-type PTEN gene in Cos1 and Rat1 cells. Furthermore, insulin-induced phosphorylation of Akt in HIRc cells was decreased more greatly by transfection of SNP1 PTEN gene than that of wild-type PTEN gene. These findings suggest that the change of C to G at position -9 of the PTEN gene is associated with the insulin resistance of type 2 diabetes due possibly to a potentiated hydrolysis of the PI3-kinase product.     

Effect of dietary fish oil on mouse testosterone level and the distribution of eicosapentaenoic acid-containing phosphatidylcholine in testicular interstitium

Low levels of serum testosterone are characteristically associated with diabetes, coronary atherosclerosis, obstructive sleep apnea, rheumatoid arthritis, and chronic obstructive pulmonary disease. Testosterone replacement therapy is effective against many of these disorders, indicating the importance of maintaining a healthy testosterone level. In this study, we investigated the effects of fish oil on murine testosterone metabolism and analyzed the dynamics of relevant lipids in testes by matrix-assisted laser desorption ionization mass spectrometry imaging. Testosterone was upregulated in mice that received fish oil. In the testicular interstitium, eicosapentaenoic acid-containing phosphatidylcholine was distributed characteristically. These data suggest that eicosapentaenoic acid is involved in testosterone metabolism.     

Electron cryomicroscopic visualization of PomA/B stator units of the sodium-driven flagellar motor in liposomes

A motor protein complex of the bacterial flagellum, PomA/B from Vibrio alginolyticus, was reconstituted into liposomes and visualized by electron cryomicroscopy. PomA/B is a sodium channel, composed of two membrane proteins, PomA and PomB, and converts ion flux to the rotation of the flagellar motor. Escherichia coli and Salmonella have a homolog called MotA/B, which utilizes proton instead of sodium ion. PomB and MotB have a peptidoglycan-binding motif in their C-terminal region, and therefore PomA/B and MotA/B are regarded as the stator. Energy filtering electron cryomicroscopy enhanced the image contrast of the proteins reconstituted into liposomes and showed that two extramembrane domains with clearly different sizes stick out of the lipid bilayers on opposite sides. Image analysis combined with gold labeling and deletion of the peptidoglycan-binding motif revealed that the longer one, approximately 70 A long, is likely to correspond to the periplasmic domain, and the other, about half size, to the cytoplasmic domain.     

Synthesis of both enantiomers of hydroxypipecolic acid derivatives equivalent to 5-azapyranuronic acids and evaluation of their inhibitory activities against glycosidases

We have synthesized 3-hydroxy- and 3,4,5-trihydroxypipecolic acid derivatives corresponding to 5-aza derivatives of uronic acids and evaluated their inhibitory activities against various glycosidases including beta-glucuronidase. Compounds 4 and 5 were chosen as common intermediates for the synthesis of 3,4,5-trihydroxypipecolic acids and 3-hydroxypipecolic acids as well as for 3-hydroxybaikiain, a unique natural product isolated from a toxic mushroom. Cross aldol reaction of N-Boc-allylglycine derivative with acrolein followed by the ring-closing metathesis gave 4 and 5 as a mixture of diastereomers which could be separated by silica gel column chromatography. By employing lipase-catalyzed kinetic resolution, the synthesis of both L- and D-isomers of 3,4,5-trihydroxy- and 3-hydroxypipecolic acids was achieved. None of the compounds tested showed inhibitory activity against alpha- and beta-glucosidases. On the other hand, L-23 and L-29 were found to have potent inhibitory activity against beta-glucuronidase. In addition, it is interesting that some uronic-type azasugar derivatives showed moderate inhibitory activities against beta-N-acetylglucosaminidase.     

Characterization of the molecular interaction between tropoelastin and DANCE/fibulin-5

Fibulin-5 is believed to play an important role in the elastic fiber formation. The present experiments were carried out to characterize the molecular interaction between fibulin-5 and tropoelastin. Our data showed that the divalent cations of Ca(2+), Ba(2+) and Mg(2+) significantly enhanced the binding of fibulin-5 to tropoelastin. In addition, N-linked glycosylation of fibulin-5 does not require for the binding to tropoelastin. To address the fibulin-5 binding site on tropoelastin constructs containing, exons 2-15 and exons 16-36, of tropoelastin were used. Fibulin-5 binding was significantly reduced to either fragment and also to a mixture of the two fragments. These results suggested that the whole molecule of tropoelastin was required for the interaction with fibulin-5. In co-immunoprecipitation experiments, tropoelastin binding to fibulin-5 was enhanced by an increase of temperature and sodium chloride concentration, conditions that enhance the coacervation of tropoelastin. The binding of tropoelastin fragments to fibulin-5 was directly proportional to their propensity to coacervate. Furthermore, the addition of fibulin-5 to tropoelastin facilitated coacervation. Taken together, the present study shows that fibulin-5 enhances elastic fiber formation in part by improving the self-association properties of tropoelastin.